Then I patched again, and saw arc patch try to find commit quack to patch on top of:

epriestley@orbital ~/dev/scratch/lock-ssh $ arc patch D223
Created and checked out branch arcpatch-D223.
This diff is against commit quack, but the commit is nowhere in the
working copy. Try to apply it against the current working copy state?
(e71424e6f177b9859dd77fcaaba4530dd1439f72) [Y/n]